Radio-frequency (RF) shielding is often required for semiconductor devices, to protect the device from electromagnetic interference (EMI) which degrades device performance. In semiconductor device packages where the device is attached to a multilayer substrate, the substrate generally includes insulating layers and conducting layers. The conducting layers are typically copper wiring layers including a plurality of conductive traces. Effective RF shielding requires that a shield covering the top of the device (e.g. a conformal metal coating) make electrical connection to a trace providing shielding beneath the device. This in turn generally requires cutting into the package and partially through the substrate to expose the trace intended to connect with the conductive coating. Since a typical trace is a layer of copper with a thickness of only about 18 μm, this cutting process has a narrow process window; controlling the depth of the cut may add time and cost to the overall manufacturing process.
In addition, shielding the sides of a package generally requires that the packages be at least partially singulated (laterally separated from each other). It is desirable, however, to apply the shielding to an array of packages, as opposed to one package at a time. The process for applying the shielding is preferably completed prior to full singulation.
It therefore is desirable to implement a process for RF shielding of laminated packages which has a wide process window and results in a fully shielded, singulated package.